From: Weijie Yang <weijie.yang.kh@gmail.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>, Michal Hocko <mhocko@suse.cz>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: swap: Use swapfiles in priority order
Date: Fri, 14 Feb 2014 21:33:17 +0800 [thread overview]
Message-ID: <CAL1ERfMnN28X4wj-jS90kL3syPmup4VUMh45D_A=0WQq2xYO1A@mail.gmail.com> (raw)
In-Reply-To: <20140214101742.GY6732@suse.de>
On Fri, Feb 14, 2014 at 6:17 PM, Mel Gorman <mgorman@suse.de> wrote:
> On Thu, Feb 13, 2014 at 11:58:05PM +0800, Weijie Yang wrote:
>> On Thu, Feb 13, 2014 at 6:42 PM, Mel Gorman <mgorman@suse.de> wrote:
>> > According to the swapon documentation
>> >
>> > Swap pages are allocated from areas in priority order,
>> > highest priority first. For areas with different priorities, a
>> > higher-priority area is exhausted before using a lower-priority area.
>> >
>> > A user reported that the reality is different. When multiple swap files
>> > are enabled and a memory consumer started, the swap files are consumed in
>> > pairs after the highest priority file is exhausted. Early in the lifetime
>> > of the test, swapfile consumptions looks like
>> >
>> > Filename Type Size Used Priority
>> > /testswap1 file 100004 100004 8
>> > /testswap2 file 100004 23764 7
>> > /testswap3 file 100004 23764 6
>> > /testswap4 file 100004 0 5
>> > /testswap5 file 100004 0 4
>> > /testswap6 file 100004 0 3
>> > /testswap7 file 100004 0 2
>> > /testswap8 file 100004 0 1
>> >
>> > This patch fixes the swap_list search in get_swap_page to use the swap files
>> > in the correct order. When applied the swap file consumptions looks like
>> >
>> > Filename Type Size Used Priority
>> > /testswap1 file 100004 100004 8
>> > /testswap2 file 100004 100004 7
>> > /testswap3 file 100004 29372 6
>> > /testswap4 file 100004 0 5
>> > /testswap5 file 100004 0 4
>> > /testswap6 file 100004 0 3
>> > /testswap7 file 100004 0 2
>> > /testswap8 file 100004 0 1
>> >
>> > Signed-off-by: Mel Gorman <mgorman@suse.de>
>> > ---
>> > mm/swapfile.c | 2 +-
>> > 1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/mm/swapfile.c b/mm/swapfile.c
>> > index 4a7f7e6..6d0ac2b 100644
>> > --- a/mm/swapfile.c
>> > +++ b/mm/swapfile.c
>> > @@ -651,7 +651,7 @@ swp_entry_t get_swap_page(void)
>> > goto noswap;
>> > atomic_long_dec(&nr_swap_pages);
>> >
>> > - for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
>> > + for (type = swap_list.head; type >= 0 && wrapped < 2; type = next) {
>>
>> Does it lead to a "schlemiel the painter's algorithm"?
>> (please forgive my rude words, but I can't find a precise word to describe it
>> because English is not my native language. My apologize.)
>>
>> How about modify it like this?
>>
>
> I blindly applied your version without review to see how it behaved and
> found it uses every second swapfile like this
I am sorry to waste your time, I should have tested it.
I will review the code more carefully, and send a tested patch if I find a
better way.
Apologize again.
> Filename Type Size Used Priority
> /testswap1 file 100004 100004 8
> /testswap2 file 100004 16 7
> /testswap3 file 100004 100004 6
> /testswap4 file 100004 8 5
> /testswap5 file 100004 100004 4
> /testswap6 file 100004 8 3
> /testswap7 file 100004 100004 2
> /testswap8 file 100004 23504 1
>
> I admit I did not review the swap priority search algorithm in detail
> because the fix superficially looked straight forward but this
> alternative is not the answer either.
>
> --
> Mel Gorman
> SUSE Labs
next prev parent reply other threads:[~2014-02-14 13:33 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-13 10:42 [PATCH] mm: swap: Use swapfiles in priority order Mel Gorman
2014-02-13 15:58 ` Weijie Yang
2014-02-14 10:17 ` Mel Gorman
2014-02-14 13:33 ` Weijie Yang [this message]
[not found] ` <loom.20140214T135753-812@post.gmane.org>
[not found] ` <CABdxLJHS5kw0rpD=+77iQtc6PMeRXoWnh-nh5VzjjfGHJ5wLGQ@mail.gmail.com>
2014-02-24 8:28 ` Hugh Dickins
2014-04-12 21:00 ` [PATCH 0/2] swap: simplify/fix swap_list handling and iteration Dan Streetman
2014-04-12 21:00 ` [PATCH 1/2] swap: change swap_info singly-linked list to list_head Dan Streetman
2014-04-23 10:34 ` Mel Gorman
2014-04-24 0:17 ` Shaohua Li
2014-04-24 8:30 ` Mel Gorman
2014-04-24 18:48 ` Dan Streetman
2014-04-25 4:15 ` Weijie Yang
2014-05-02 20:00 ` Dan Streetman
2014-05-04 9:39 ` Bob Liu
2014-05-04 20:16 ` Dan Streetman
2014-04-25 8:38 ` Mel Gorman
2014-04-12 21:00 ` [PATCH 2/2] swap: use separate priority list for available swap_infos Dan Streetman
2014-04-23 13:14 ` Mel Gorman
2014-04-24 17:52 ` Dan Streetman
2014-04-25 8:49 ` Mel Gorman
2014-05-02 19:02 ` [PATCHv2 0/4] swap: simplify/fix swap_list handling and iteration Dan Streetman
2014-05-02 19:02 ` [PATCHv2 1/4] swap: change swap_info singly-linked list to list_head Dan Streetman
2014-05-02 19:02 ` [PATCH 2/4] plist: add helper functions Dan Streetman
2014-05-12 10:35 ` Mel Gorman
2014-05-02 19:02 ` [PATCH 3/4] plist: add plist_rotate Dan Streetman
2014-05-06 2:18 ` Steven Rostedt
2014-05-06 20:12 ` Dan Streetman
2014-05-06 20:39 ` Steven Rostedt
2014-05-06 21:47 ` Dan Streetman
2014-05-06 22:43 ` Steven Rostedt
2014-05-02 19:02 ` [PATCH 4/4] swap: change swap_list_head to plist, add swap_avail_head Dan Streetman
2014-05-05 15:51 ` Dan Streetman
2014-05-05 19:13 ` Steven Rostedt
2014-05-05 19:38 ` Peter Zijlstra
2014-05-09 20:42 ` [PATCH] plist: make CONFIG_DEBUG_PI_LIST selectable Dan Streetman
2014-05-09 21:17 ` Steven Rostedt
2014-05-12 11:11 ` [PATCH 4/4] swap: change swap_list_head to plist, add swap_avail_head Mel Gorman
2014-05-12 13:00 ` Dan Streetman
2014-05-12 16:38 ` [PATCHv3 0/4] swap: simplify/fix swap_list handling and iteration Dan Streetman
2014-05-12 16:38 ` [PATCHv2 1/4] swap: change swap_info singly-linked list to list_head Dan Streetman
2014-05-12 16:38 ` [PATCH 2/4] plist: add helper functions Dan Streetman
2014-05-12 16:38 ` [PATCHv2 3/4] plist: add plist_requeue Dan Streetman
2014-05-13 10:33 ` Mel Gorman
2014-05-12 16:38 ` [PATCHv2 4/4] swap: change swap_list_head to plist, add swap_avail_head Dan Streetman
2014-05-13 10:34 ` Mel Gorman
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